Generally, bolts and nuts couple two structures to each other or are used as a fastener which fasten a structure to another coupling body such that the coupling body penetrates a fastening hole with screw threads formed therein. In many cases, when such bolts are used for fastening, nuts are used alone to fix products and, when firm fixing is needed, double nuts or anti-loosening nuts are used.
As currently used anti-loosening nuts, U-type nuts, nylon nuts, Teflon nuts, spring washer nuts, T nuts (T-lock nuts), Nord-lock nuts, ERM nuts, double nuts, OT nuts, Hard-lock nuts, hyper nuts, and the like have been widely used in various applications and according to various methods.
As the related art, Korean Patent Application Registration No. 10-0701782 (ANTI-LOOSENING NUT, Registration date: Mar. 24, 2007) discloses an anti-loosening nut that can prevent a bolt from being loosened, by using a coil spring installed in an inner circumferential surface of the nut.
Although such technique for using an anti-loosening nut accommodating a bolt, as described above, is disclosed, the original fastening state is not maintained due to vibration, impact, or the like at a portion in which the bolt is fastened to a fastening hole formed in a parent material of a structure not requiring a nut and the bolt slides and is thus loosened.
In particular, an anti-loosening bolt, which is provided at a main body thereof with a tap for bonding a spring to accommodate a coil spring and prevents the bolt from being loosened, by a fastening force of the coil spring, is disclosed.
As the related art, Korean Patent Application Publication No. 10-2003-0000409 (ANTI-LOOSENING BOLT DEVICE, Publication date: Jan. 6, 2003) discloses an anti-loosening bolt device that prevents a bolt/nut fastened to a structure from being loosened.
However, when such anti-loosening bolts are used in main parts of railways on which vibration continuously occurs, connection parts of bridges, steel towers frequently shaken by wind, rides with a lot of shaking, and the like in which human safety is most important, the bolts are loosened and thus accidents frequently happen. In addition, when maintenance or checkup is needed, nuts must be unscrewed and fastened again, which makes handling or use thereof difficult.